1976 911 leaking heat exchangers - Carbon Monoxide

[SunburntLobster]

Hi
Out of interest I chucked a cheap carbon monoxide meter in my cabin in the passenger footwell (I know it should be higher but my theory is this is the closest to where the inlet duct is) this morning and within a mile it started beeping at me!

Looks like it was taking readings of 100-150 p.p.m - obviously not good...

I have the windows down and all air distribution levers closed.

I assume the heat exchangers are rotten out on the inside, for the time being can I disconnect the hose and cap off the heat exchangers?

Probably another good reason why I should also buy and install the engine tinware to prevent as much gas getting back into the engine bay.

Anyone else checked their car recently?

[75 911s]

Sounds like the right time to upgrade to SSI. I take it they are the original stock heat exchangers? If so, those heat exchangers were a terrible compromise and is one of the worst performing exhaust of all air cooled 911s. I often see cracks and holes in the heat boxes as well.

Do your flapper boxes work and are the tubes from the exchangers to the flapper boxes sound?

[SunburntLobster]

Hi - yup original H.E
I backdated the heating so it has all new aircraft grade ducting to and from the HE. The flapper box did seem to be closing however it is unlikely to be gas-tight, there is no heat in the cabin either so wonder if it has found another way in (trans tunnel?)

[Joe Bob]

Your HEs aren't the source of CO but a vector for the CO to enter the cabin. You have an exhaust leak.